First of all, i strongly join the people who recommended using Perl::Critic. It is an excellent to improve your style

Actually, using Perl::Critic doesn't help you to improves one style. It will however help you mimic the style of the people in charge of Perl::Critic.

my ($self) = @_; # You should probably write:
my ($self) = shift; # Option 1.
my ($self) = $_[0]; # Option 2. The two options do a very similar thin
+g, choose the one that suits you and make sure you understand what th
+ey mean.
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I loathe this kind of advice. You give two alternatives to a line, without any explanation of why any of the alternatives are better. I certainly don't see any problem with the first line than any of the alternatives solves.

for (my $i = 1; $i <= $size; $i++) # This is OK, but it is C style, no
+t Perl.
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It's Perl. Hence, it's Perl style. Just because it looks like C doesn't mean it's bad.

for my $i (1 .. $size) # This is more Perlish and more readable. It's 
+a matter of taste.
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If it's a matter of taste, why recommend one over the other?

Personally, I also look at the body when deciding what kind of loop to use. In this case, I wouldn't use a for statement at all.

$self->{allowed} = [undef, (1) x $size];
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I suspect $self->{allowed}[0] is never used, but I didn't look at the code a lot. If it's not used, I wouldn't use the undef in the code above.